I'm referring to bitcoin specifically, as I was specifically trying to determine whether or not it's a good idea to hold BTC right now. I'm obviously more bullish than 5% on "future blockchain technology that replaces it" (such as Ethereum or others)"; if I wasn't I would not be a full-time member of the industry :)

If you do that you can change the equation from Bitcoin winning and continuing to have value, versus the blockchain technology succeeding and some instance of it continuing to have value.

But then, the question becomes: if you're bullish in blockchain tech, but not bitcoin, then why not invest exclusively in the other blockchain tech and not bitcoin?